net.sf.saxon.expr

## Class SimpleStepExpression

- java.lang.Object
- - net.sf.saxon.expr.Expression
  - - net.sf.saxon.expr.SlashExpression
    - - net.sf.saxon.expr.SimpleStepExpression

- All Implemented Interfaces:
    Serializable, SourceLocator, LocationProvider, SaxonLocator, ContextMappingFunction<Item>, ContextSwitchingExpression, InstructionInfo, Locator

      public final class SimpleStepExpression
      extends SlashExpression

  An SimpleStepExpression is a special case of a SlashExpression in which the start expression selects a single item (or nothing), and the step expression is a simple AxisExpression. This is designed to avoid the costs of creating a new dynamic context for expressions (common in XQuery) such as for $b in EXPR return $b/title
  See Also:
    Serialized Form

- - ### Field Summary

    - ### Fields inherited from class net.sf.saxon.expr.Expression

      `EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, INHERITED_CONTEXT, INSPECTION_CONTEXT, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, NAVIGATION_CONTEXT, NODE_VALUE_CONTEXT, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, W3C_CONSUMING, W3C_FREE_RANGING, W3C_GROUP_CONSUMING, W3C_MOTIONLESS, WATCH_METHOD`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `SimpleStepExpression(Expression start, Expression step)`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `Expression` | `copy()` Copy an expression.
    `ExpressionCompiler` | `getExpressionCompiler()` Return the compiler of the SimpleStep expression
    `SequenceIterator` | `iterate(XPathContext context)` Evaluate the expression, returning an iterator over the result
    `Expression` | `optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` Perform optimisation of an expression and its subexpressions.
    `Expression` | `typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` Type-check the expression

    - ### Methods inherited from class net.sf.saxon.expr.SlashExpression

      `addToPathMap, computeCardinality, computeDependencies, computeSpecialProperties, equals, explain, getControlledExpression, getControllingExpression, getFirstStep, getIntegerBounds, getItemType, getLastStep, getLeadingSteps, getRemainingSteps, getStep, getStreamability, getStreamingAdjunct, hashCode, isAbsolute, isInheritedAttributePath, isPermittedAxis, iterateSubExpressionInfo, iterateSubExpressions, map, promote, promoteFocusIndependentSubexpressions, replaceSubExpression, setStartExpression, setStepExpression, simplify, toPattern, toStreamingPattern, toString, tryToMakeAbsolute`

    - ### Methods inherited from class net.sf.saxon.expr.Expression

      `adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getExpressionName, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError`

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Constructor Detail

    - #### SimpleStepExpression

          public SimpleStepExpression(Expression start,
                              Expression step)

  - ### Method Detail

    - #### typeCheck

          public Expression typeCheck(ExpressionVisitor visitor,
                             ExpressionVisitor.ContextItemType contextItemType)
                               throws XPathException

      Description copied from class: `SlashExpression`
      Type-check the expression
      Overrides:
        `typeCheck` in class `SlashExpression`
      Parameters:
        `visitor` - an expression visitor
        `contextItemType` - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to `Type.ITEM_TYPE`
      Returns:
        the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
      Throws:
        `XPathException` - if an error is discovered during this phase (typically a type error)

    - #### optimize

          public Expression optimize(ExpressionVisitor visitor,
                            ExpressionVisitor.ContextItemType contextItemType)
                              throws XPathException

      Description copied from class: `Expression`
      Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

      This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

      Overrides:
        `optimize` in class `SlashExpression`
      Parameters:
        `visitor` - an expression visitor
        `contextItemType` - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to `Type.ITEM_TYPE`
      Returns:
        the original expression, rewritten if appropriate to optimize execution
      Throws:
        `XPathException` - if an error is discovered during this phase (typically a type error)

    - #### copy

          public Expression copy()

      Copy an expression. This makes a deep copy.
      Overrides:
        `copy` in class `SlashExpression`
      Returns:
        the copy of the original expression

    - #### iterate

          public SequenceIterator iterate(XPathContext context)
                                   throws XPathException

      Evaluate the expression, returning an iterator over the result
      Overrides:
        `iterate` in class `SlashExpression`
      Parameters:
        `context` - the evaluation context
      Returns:
        a SequenceIterator that can be used to iterate over the result of the expression
      Throws:
        `XPathException` - if any dynamic error occurs evaluating the expression

    - #### getExpressionCompiler

          public ExpressionCompiler getExpressionCompiler()

      Return the compiler of the SimpleStep expression
      Overrides:
        `getExpressionCompiler` in class `SlashExpression`
      Returns:
        the relevant ExpressionCompiler

Copyright (c) 2004-2013 Saxonica Limited. All rights reserved.